1. Field of the Invention
The present invention relates to a semiconductor device which is formed by sealing a semiconductor chip in a package of resin, ceramic or the like for shipment. More particularly, the present invention relates to a semiconductor device which is provided with a circuit for protecting the semiconductor chip from overcurrent.
2. Description of the Prior Art
An example of such a circuit in the prior art is shown in FIG. 1. As shown, a protective circuit comprising diodes D.sub.1 and D.sub.2 and a resistor R is connected between a lead pin 1 provided outside the package and the semiconductor chip 2 inside the package. When a negative overvoltage is applied to the lead pin 1, an overcurrent caused by the overvoltage is allowed to flow through the diode D.sub.1 from the earth side so that the semiconductor chip 2 will never be adversely affected. When, on the other hand, a positive voltage is applied to the lead pin 1, the resultant overcurrent is allowed to flow through the diode D.sub.2 to the power source V so that in this case the semiconductor chip 2 also will never be adversely affected.
However, the above-described conventional semiconductor device suffers from the following problems. Namely, since it is necessary to provide one resistor and two diodes, the circuit is relatively intricate, and the number of components is unnecessarily large. Also, the high frequency characteristic of the device is lowered by the capacitance of the diodes.
Another example of protecting means for protecting a semiconductor chip from overcurrent comprises a current monitoring circuit provided between an external terminal to which overcurrent may be applied and a signal source (external circuit) for monitoring overcurrent. However, since in this method it is necessary to connect a resistor so as to cause a voltage drop between the external terminal and the signal source, it is rather difficult to apply a sufficiently large signal to the semiconductor chip through the external terminal during ordinary operation.